Reptiles and Amphibians of Thailand

Thailand's Snakes, Lizards, Turtles, and Frogs

Yellow-spotted Mountain Stream Snake

Opisthotropis maculosa

This species is found in Thailand, but not within Bangkok itself
Yellow-spotted Mountain Stream Snake Keelback Opisthotropis maculosa งูลายสอจุดเหลือง thailand Nong Khai
The only known specimen of Yellow-spotted Mountain Stream Snake (© Bryan Stuart)

English name: Yellow-spotted Mountain Stream Snake (aka: “Yellow-spotted Mountain Keelback”)
Scientific name: Opisthotropis maculosa
Thai name: งูลายสอจุดเหลือง (Ngu Lay Sor Jud Leuang)

Description: 52cm long. Has a small head indistinct from the neck and small eyes. Glossy black body with a yellow spot on every scale. Top of head is black with white speckling at the edges. Belly is yellow including chin shields and subcaudals.

Relevant scale counts: 15 midbody scale rows. Scales are smooth. 7 supralabials with 4th supralabial in contact with the eye, prefrontal is in contact with supraocular, frontal is not in contact with preocular, 2nd pair of chin shields longer than 1st pair, 182 ventral scales and 67 subcaudals in the single known specimen (male).

Similar Species: Hai Ha Mountain Stream Snake has yellow chin shields with brownish-black mottling, 8-9 supralabials with the 4th and 5th in contact with the eye, prefrontal not in contact with supraocular, frontal touching preocular, 1st pair of chin shields longer than 2nd pair, 164-169 ventrals and 75-79 subcaudals in females, and is only known from Vietnam and China.

Hung-Ta Chang’s Mountain Stream Snake has yellow chin shields with brownish-black mottling, 7 supralabials with 4th and 5th in contact with eye, prefrontal not in contact with supraocular, frontal touching preocular, 1st pair of chin shields longer than or equal to 2nd pair, 170–189 ventrals and 76-98 subcaudals in males and 168–175 ventrals and 69-84 subcaudals in females,. It is only known from China.

Range: Has only been found at a single locality in Nong Khai Province in Thailand.

Habitat: The only specimen was found swimming at night in a temporary stream in mixed forest at 190m elevation.

Place in the ecosystem: Diet is unknown but it likely feeds of fish, frogs, earthworms, and/or crustaceans as other members of its genus are known to do. Would be eaten by larger snakes and monitors.

Danger to humans: Is a rear-fanged snake but its venom properties and potential danger are unknown.

Conservation status and threats: As only one specimen has been found, its conservation status is unknown. The lack of other finds is worrisome for the continued survival of the species.

Interesting facts: After the Yellow-spotted Mountain Stream Snake was discovered in Thailand in 2007, similar snakes which appeared to be the same species were discovered in Vietnam and southern China. However, in 2017 genetic studies proved that the Vietnam specimen was actually a separate species, which was named the Hai Ha Mountain Stream Snake. Then in 2020 genetic studies proved that the Chinese specimens were split, with the southernmost one turning out to also be the Hai Ha Mountain Stream Snake while the rest were yet another new species, Hung-Ta Chang’s Mountain Stream Snake. In appearance they can only be distinguished by scale counts and different coloration on the bottom of the head.

References:
A New Opisthotropis from Northeastern Thailand
A new species of Opisthotropis from northern Vietnam previously misidentified as the Yellow-spotted Mountain Stream Keelback
Re-examination of the Chinese record of Opisthotropis maculosa, resulting in the first national record of O. haihaensis and description of a new species
Thai National Parks: Yellow-spotted Mountain Stream Snake

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